Fuel pump issues in 1993 80 series

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May 23, 2022
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Well first of all im quite new here but ive seen some good advice on different people asking questions about there fuel pump issues.
I own a 1993 Landcruiser (FZJ80) Petrol. I have a crank but no start issue. I have been trying to diagnose the issue myself with no hope. The information I have currently may be helpful to a few of you who understand a bit more about the electrical side of a car then me.

First of all I am getting no fuel to my fuel rail while car is in the ON position and also while cranking in the START position. I went out and brought a new fuel pump with no hope. From here I decided that I wasnt gonna go out and spend money on everything fuel issues before I knew what it was. I went back to the fuel pump which is under the rear passenger seats. I noticed that there was no power going to the fuel pump at all, But take note there is 12V going to the fuel gauge showing how much fuel I have in the tank. This got me thinking maybe it was a Fuel pump relay issue or a Circuit opening relay issue. I felt my Circuit opening relay click on every time I turned the car into the ON position which that seems all fine. I couldnt do the fuel pump relay by myself but I did have a multi meter to test for ohms which it was about 80 ohms and I read somewhere between 50-120 ohms was ok for those coils.

After all of that I turned my attention to the fuel pump resistor (Which I didnt know these cars had one but found it reading about fuel pump wiring). I tested the ohms on this too which it was recommended for 0.73 ohms and I got around 0.79 ohms which I thought ok that seems good enough. Now im a bit confused on what it could be.

I had a little look online and found out I was able to give the fuel pump 12V from the diagnoses by jumping B+ and FP, In my surprise this worked and the car was starting. But I dont wanna drive on that. On the same forum I read they said this bypass the fuel pump relay and resistor. (Im not sure about the Opening circuit relay).

Now I am currently stuck on what to do next? Any help would be nice!

(I understand this is a bit long but im just trying to give all the information I have about this issue to someone with a bit more knowledge then me to help me out)
 
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I am getting no fuel to my fuel rail while car is in the ON position and also while cranking in the START position.
That points to the circuit opening relay, fuel pump relay, and associated wiring.
The COR has 2 coils. The primary coil energizes from the STARTER circuit, the secondary energizes from the flap in the AFM when the engine begins to suck air.
The COR feeds +12 to the FPR and the FPR is energized by a logic low from the ECU.
The complete 1994 schematics are available to download from the resources section. Same as 1993.
I would first verify that pin 2 of the COR is getting +12 with the key in the ON/RUN position.
Then you can start bypassing relays to isolate the issue.

By jumping FP-B+ in the diagnostic connector you have bypassed all fuel pump logic and the pump will run whenever the key is in the ON/RUN position. This is potentially dangerous as the pump will continue to run in the event of a collision.
 
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Reach into your airflow meter and manually open the flapper door with the key in the ON position. Does the fuel pump turn on? If so, then your problem most likely lies in the park/neutral safety switch, as that is what powers the first relay coil in the circuit opening relay (the afm turns on the circuit opening relay through the secondary relay coil).

If the pump does not turn on, then your issue is most likely the circuit opening relay. Check to make sure you have 12v at pin 2 (Yellow/Red) of the circuit opening relay. If so, jump pin 1 (Red/Green) and pin 2 (Yellow/Red). That should turn on the pump.

Try those tests and report back.
 
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Reach into your airflow meter and manually open the flapper door with the key in the ON position. Does the fuel pump turn on? If so, then your problem most likely lies in the park/neutral safety switch, as that is what powers the first relay coil in the circuit opening relay (the afm turns on the circuit opening relay through the secondary relay coil).
If the NSS was the issue, the starter would not crank.
 
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Alright ill do another double checking today after work, but thank you for your replys. I did what john had said in his first reply. But i didnt quite know what pins to test in the opening circuit relay. (Check to make sure you have 12v at pin 2 (Yellow/Red) of the circuit opening relay. If so, jump pin 1 (Red/Green) and pin 2 (Yellow/Red)) this is helpful thankyou!!
I will be able to test the COR correctly now!

I also tested the fuel pump relay for power at the connector when the key was turned ON and can confirm there is no power going to it.

Also this car has a VAF sensor im guessing it kinda does the same thing. But this is getting power to it if that helps.

I’ll update everyone after work with your suggestions!
 
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Alright ill do another double checking today after work, but thank you for your replys. I did what john had said in his first reply. But i didnt quite know what pins to test in the opening circuit relay. (Check to make sure you have 12v at pin 2 (Yellow/Red) of the circuit opening relay. If so, jump pin 1 (Red/Green) and pin 2 (Yellow/Red)) this is helpful thankyou!!
I will be able to test the COR correctly now!

I also tested the fuel pump relay for power at the connector when the key was turned ON and can confirm there is no power going to it.

Also this car has a VAF sensor im guessing it kinda does the same thing. But this is getting power to it if that helps.

I’ll update everyone after work with your suggestions!
The FPR should not have +12 on pin 5 with the key in the ON position unless the COR is energized or jumped.
 
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I had the same issue awhile back and the Circuit Opening Relay tested fine too, plus I found the same situation where it would start/run only with the FP-B+ jumper so I tried a friend’s COR and the truck started. I immediately replaced the COR with a new one and my starting issues went away but the “bad one” definitely tested fine in my case
 
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Alright I have some information, Which is interesting.

On the COR Pin 2 which is the yellow/red wire has no voltage when the key is on the ON switch.

Multimeter connected to Pin 2 and then to a ground connection which is right next to the relay box under the dash.

So im not getting any power to the COR (From the original post I must of been feeling another relay clicking on).

I could try a different COR from one of my friends but if im not getting any power it kinda rules it out.

Any ideas on what to do next? Possibly wiring?
 
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The power to pin 2 is supplied by the EFI main relay. That has to be working properly because it supplies power to everything, includimg the b+ terminal of the diagnostic port, which you verified has power by jumping to the FP terminal to run the pump. Besides, the engine wouldn't run if the EFI relay wasn't working.

You must have a bad wire or connector pin problem in a plug. The wire goes from pin 2 on the COR, to plug IH1, then to splice point E9, where it meets up with the main EFI relay voltage. Since splice E9 also branches off to b+ on the diagnostic port, we know everything upstream of E9 is good. The problem lies between E9 splice and the COR on the Yellow/Red wire.

The next step would be to find the IH1 connector as your half way point. Check if you have 12v on both sides of the connector with it plugged in. Voltage on both sides - check wire from it to COR. No voltage on either side - check wire from it to splice E9. Voltage on only one side - clean the pins.
 
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Problem solved!

Thank you to all the helpful people.
It was indeed a wiring issue.
There was a LPG kit installed on the car before I had bought it.
The previous owner told me that he took out the kit. He obviously just took out all of the main components and not the wiring. The same wire must of supplied power to the LPG kit.

There was a relay between the COR and the power line (Yellow/red wire) The fuse here had blown. I decided since there was no LPG kit installed just to rewire myself.

I did confirm that the other wires connected to this relay was for the LPG (Incase anyone thought I might short a ground or something)

Quite a silly mistake from me as I thought a stock part was messing with something!

Anyway learnt quite a bit about the fuel pump circuit so Thank you for the knowledge!
 

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